1. Field of the Invention
The present invention relates to an automotive air bag system for protecting a passenger from injuring by an impact of a collision and, more specifically to the automotive air bag system with an inflator for inflating an air bag at a slow speed.
2. Description of the Related Art
As is generally known, an automotive air bag system has an air bag inflator which generates a gas quickly when a high acceleration is imparted to a vehicle due to, for example, a collision of the vehicle against an obstacle. The air bag is inflated under various conditions requiring different inflating speeds. Various inflating speed controllers have been proposed in, for example, JP-A Nos. 5-24498 and 7-251694, and JP-U No. 6-1029.
The inflating speed controller proposed in JP-A No. 5-24498 controls the inflating speed of the air bag by operating a valve plate by a gas generated by an inflator to control the amount of intake air by closing an air inlet opening formed in a holding box when the ambient temperature is high so that the air bag can be inflated at a substantially fixed inflating speed regardless of the variation of the ambient temperature.
The inflating speed controller proposed in JP-U No. 6-1029 controls the inflating speed of the air bag by breaking a resin plate formed on an air bag case by an internal pressure of the air bag to reduce the internal pressure of the air bag to avoid imparting an excessively high impact on a vehicle passenger the suddenly inflating air bag when the air bag is unable to inflate smoothly at the initial stage of inflation and starts inflating suddenly due to the sharp increase of the internal pressure of the air bag.
The inflating speed controller proposed in JP-A No. 7-251694 supplies a gas generated by an inflator through a narrow passage to an air bag to inflate the air bag at a relatively low inflating speed at the initial stage of combustion in the inflator, and removes a baffle plate disposed in the gas passage by the pressure of the gas increasing with the progress of combustion in the inflator to expand the gas passage so that the inflating speed of the air bag is increased to avoid imparting a sudden impact to an infant or a vehicle passenger by the sudden inflation of the air bag at the initial stage of inflation.
No prior art inflating speed controllers can control the inflation of the air bag properly and the air bag is inflated at an excessively high inflating speed when the vehicle collides lightly against an obstacle while the vehicle is traveling at a relatively low traveling speed and a relatively light shock is exerted on the vehicle. Generally, the air bag is provided with a gas discharging hole to absorb energy moderately, and the air bag is held fully inflated only a very short time. The data on the air bag are determined for appropriately securing the passenger from a strong impact that may be imparted to the passenger when the vehicle collides with an obstacle while traveling at a very high speed. Therefore, the passenger will plunge into the air bag after the air bag has been fully inflated and has started deflating if the vehicle collides against an obstacle with a relatively low impact while the same is traveling at a low traveling speed, and the function of the air bag may not fully be utilized.